GaussianCity is a framework focused on efficiently generating boundless 3D cities, based on 3D Gaussian rendering technology. This technology, through compact 3D scene representation and a spatially aware Gaussian attribute decoder, solves the memory and computational bottlenecks encountered by traditional methods when generating large-scale city scenes. Its main advantage is the ability to quickly generate large-scale 3D cities in a single forward pass, significantly outperforming existing technologies. This product was developed by the S-Lab team at Nanyang Technological University, with the related paper published in CVPR 2025. The code and models have been open-sourced and are suitable for researchers and developers who need to efficiently generate 3D city environments.